Typically, outdoor power tools utilize a two-stroke internal combustion engine or an electric motor for powering an implement such as a line trimmer, a blower/vacuum or a chain saw. Two-stroke engines are relatively light and may readily be carried by an operator during operation with various angular orientations. However, two-stroke engines have well-recognized exhaust emissions problems that often make them unfeasible for their use in areas that must comply with exhaust gas emissions regulations such as the California Air Resource Board (CARB) and Federal EPA regulations dealing with air quality. Four-stroke internal combustion engines, on the other hand, provide a distinct advantage for outdoor power tool manufacturers in their attempt to meet the CARB and Federal EPA emissions regulations. In addition, four-stroke engines operate more quietly as compared to two-stroke engines.
Unlike two-stroke engines, which simultaneously admit a fresh charge of fuel and air mixed with lubrication oil while exhausting combustion products, including unburned fuel, a four-stroke internal combustion engine maintains the lubricating oil relatively isolated from a combustion chamber. Four-stroke engines are typically lubricated by oil from a separate oil reservoir, either in a crankcase, which is a pan attached to an underside portion of the engine, or in an external tank. An oil dipper is coupled to an end portion of a connecting rod and operates to splash oil from the oil reservoir onto various engine components for lubrication.